The effect of modification of the carbohydrate unit of the glycopeptide on the physiological function of RBP will be pursued by using specific glycosidases. Efforts will be made to remove the entire heavy-chain carbohydrate. Since the carbohydrate is attached near the N-terminal and a glycopeptide is released by CNBr change at methionine, the possibility exists that the glycopeptide may be released, leaving the rest of the RBP intact, by adding CNBr in stoichiometric quantities under controlled conditions of pH and temperature. Removal of the exterior N-acetylglucosamine residues will be tried by using enzymes in addition to those already tested. Continued efforts to find a way to remove the exterior galactose will be made. Modifications of the periodate treatment to direct it toward the carbohydrate and away from tryptophan will be continued. Peptide mapping of the pro-RBP will be done by employing methods involving fluorescence spectroscopy. Trypsin, along with commercial proteases such as elastase and plasmin, will be tried on purified fractions of pro-RBP to attempt to "activate" this form. Total purification of the pro-RBP will be attempted. The existence of an X-pro-RBP will be considered.